Convergent transcription confers a bistable switch in Enterococcus faecalis conjugation

Abstract

Convergent gene pairs with head-to-head configurations are widespread in both eukaryotic and prokaryotic genomes and are speculated to be involved in gene regulation. Here we present a unique mechanism of gene regulation due to convergent transcription from the antagonistic prgX/prgQ operon in Enterococcus faecalis controlling conjugative transfer of the antibiotic resistance plasmid pCF10 from donor cells to recipient cells. Using mathematical modeling and experimentation, we demonstrate that convergent transcription in the prgX/prgQ operon endows the system with the properties of a robust genetic switch through premature termination of elongating transcripts due to collisions between RNA polymerases (RNAPs) transcribing from opposite directions and antisense regulation between complementary counter-transcripts. Evidence is provided for the presence of truncated RNAs resulting from convergent transcription from both the promoters that are capable of sense-antisense interactions. A mathematical model predicts that both RNAP collision and antisense regulation are essential for a robust bistable switch behavior in the control of conjugation initiation by prgX/prgQ operons. Moreover, given that convergent transcription is conserved across species, the mechanism of coupling RNAP collision and antisense interaction is likely to have a significant regulatory role in gene expression.inverse expression | overlapping DNA | gene-regulatory network

Antagonistic self-sensing and mate-sensing signaling controls antibiotic-resistance transfer

“…ematical model incorporated the underlying genetic regulation of pCF10, which entails nonlinear interactions of sense:antisense transcripts within prgQ and prgX operons and interactions of PrgX with C and I (7,11,18) and is described in detail in Supporting Information. The parameter values were obtained from experimental results and from the literature (Table S2) (7).…”

“…1) (5,6). The direct effect of C on pheromone responsive gene Q (prgQ) transcription is enhanced greatly by several co-as well as posttranscriptional mechanisms, whose cumulative effects cause the system to function as a bistable genetic switch (7). It also is noteworthy that pheromone induction increases the virulence of donor strains (8).…”

Identification of a conserved branched RNA structure that functions as a factor-independent terminator

“…A strain carrying pDM4 (Table S1), which contains a segment of pCF10 from P X −176 to +223, but does not include P Q or the prgX ORF (Fig. 1), produced abundant Anti-Q (15,16,18). The 3′ terminus of Anti-Q produced from this plasmid and from pCF10 was located at P X + 107, as determined by a 3′ RACE protocol.…”

“…Cells with the mutant Anti-Q allele were induced at a low level by small amounts of cCF10, whereas cells with a wild-type Anti-Q allele were not. Given that the pheromone induction system of pCF10 exhibits properties of a bistable switch (18), Anti-Q could reduce the sensitivity of the system to noise, either minor fluctuations in external cCF10 levels or stochastic fluxes in prgQ transcription. This would prevent unproductive mating responses.…”

cis-Antisense RNA and Transcriptional Interference: Coupled Layers of Gene Regulation

“…[13], Bacillus subtilis [26], Vibrio cholerea [12], Chlamydia trachomatis [27], Psuedomonas aeruginosa [28], Psuedomonas syringae [29], Staphylococcus aureus [30], and Sinorhizobium meliloti [31]. Increasing knowledge and information of abundance of antisense genes has caused speculation that antisense transcription is an important hidden layer of regulation [16,[32][33][34].…”